Tuning my charcoal forge

[rdennett]

I got to have some fun last weekend in the forge, but it doesn't seem to get quite hot enough. The fire pot is an old brake disk about two inches deep and I use lump charcoal, NOT briquettes. I stuck a piece of scrap steel about 3/8" in diameter into what appeared to be the hot part of the forge and pumped the bellows for a while, but I never did get it up to welding heat. I got it up to about orange (although it was a little hard to judge), but it seemed to stay there. Is this a matter of my fire not being deep enough (it wasn't much deeper than the fire pot), not enough airflow or not enough patience. My experience is mostly with coal forges, so I am basing what to do on that.

Thanks for your help,
Rob

[ThomasPowers]

How big the bellows? How big the air opening(s) in the bottom of the forge? How deep was the charcoal pile? how far up from the bottom was the "hot spot" and about a dozen more questions *you* need to answer to get anything more than a wild guess.

Example: I have problems with my truck not going fast enough---can you trouble shoot it from that much info? (would telling you it was 20 years old, 4 cylinder, gas engine, and carrying a heavy load help any?)

[rdennett]

How big the bellows? How big the air opening(s) in the bottom of the forge? How deep was the charcoal pile? how far up from the bottom was the "hot spot" and about a dozen more questions *you* need to answer to get anything more than a wild guess.

Example: I have problems with my truck not going fast enough---can you trouble shoot it from that much info? (would telling you it was 20 years old, 4 cylinder, gas engine, and carrying a heavy load help any?)

Well, the pile was about 3" deep, the bellows are about 18"x24" double lung bellows connected to a 3" dryer duct connected to 1-1/2" (nominal) pipe fittings which are attached to the bottom of the brake disc with a piece of 1"x1/4" strap acting as an air grate, so say about 1 in^2 worth of air hole. I can't really tell where the hotspot was, but I put the tip of the stock I was trying to heat about halfway down into the pot.

Assuming adequate air flow, what would the effect of a higher pile of charcoal be? Will it increase the heat significantly or will I just burn up more fuel?

Thanks,
Rob

[rdennett]

Deleted. Duplicate post.

[ThomasPowers]

Generally charcoal forges work best with a deeper pile of charcoal and less air than a coal forge would use.

When I switch my solid fuel forge from coal to charcoal I place a couple of firebricks on their narrow sides by the firepot to control the width of the fire and make it easier to get it deeper.

The object of having a deeper fuel pile is to make sure that all excess oxygen is used up before it gets to the metal. Hard to weld if the piece can oxidize. If the piece can't oxidize then with proper temp you can weld without flux!

Having the fuel is smaller chunks helps too---some folks drive the charcoal through a metal grid to subdivide it smaller---makes a mess! I usually just what the larger pieces with the forge rake.

My double lunged bellows was quite a bit larger, (about 48x48 as I recall---took 2 sheets of plywood to make it). I did a bunch of forge welding with it, also had more air space in the grate I believe---used an old cast iron drain grate.

[rdennett]

I just wanted to report my status. I have had my forge up and running for a few weekends now. I was able to forge my first pair of tongs (actually not my first pair, but the first pair that are any good) as well as a spring fuller (which I don't think is going to work out), a chisel (forged but not filed), a punch and a sort of V-shaped bottoming tool. I was also able to get it up to welding heat (accidentally, but I will take what I can get). The forge is, as I have said, an upside-down lawn mower body with a Honda brake disc set in the hole where the engine would mount and attached with one bolt. The weight of the tuyere keeps things from moving around. The tuyere is made from 1-1/2 black pipe fittings and attached to the brake disc via a flange through existing mounting holes. I placed a piece of 1 x 1/4 inch strap between the flange and the bottom of the disc to keep the coals from falling in which is pinched in place by the tuyere mounting hardware. The gap has sort of chinked itself up with ash and charcoal dust. The legs are 36" pieces of 3/4" black pipe attached to flanges which are bolted to the forge body. On each side of the fire pot, I placed a fire brick on edge which allows me to pile the coals up nicely. For the bellows, I built a double-lung bellows about 18" wide by about 2 feet long and used marine vinyl for the leather. I mounted it in a frame and attached an old shovel handle for a pump. I use lump charcoal that I get at the grocery store for the fuel.

I have to do a lot of pumping, but it seems to work pretty well. I have had trouble with it consistently heating up the metal, but I think that is a matter of the pile of coals not being deep enough. I should prep the coals by breaking them a little with a tamper that I have, but putting big chunks on top and letting them fracture on their own seems to work OK.

Anyway, thanks for your help in building the thing. I have been playing with this stuff off and on since I was 18 (I am 40 now) and I finally have an OK setup (well, I don't have a vise, but I am thinking about that.)

Thanks again,
Rob